This invention relates generally to shelves for housing printed circuit packs (PCPs) and more particularly to the provision of input and output (I/O) connectors for cable connections to PCPs housed in shelves.
Shelves for housing PCPs face significant space restrictions. This is particularly so for shelves located in a central office of a telephone switching service provider. The space available is dictated by the height, width and depth of the racks which a service provider uses for holding the shelves. It is important to provide both the maximum functionality and the maximum flexibility in the space provided.
A shelf typically has a Printed Circuit Board (PCB) extending across the rear, referred to as a backplane, which has a series of edge connectors on its front face. Either PCPs or modules are oriented perpendicular to the backplane and plugged into the edge connectors on the backplane. The edge connectors are generally generic so that a variety of different modules may alternatively be plugged into the same position in the backplane.
I/O connections for carrying input and output signals can also be made through the backplane. Typically a fixed pattern of cable connectors are mounted on the back surface of the backplane. There are several disadvantages to this mode of enabling cable connections. First, access to the cable connectors is only available from the rear of the backplane. Second, the number and type of cable connectors is fixed. This limits the combinations of modules which can be plugged into the backplane based on the type of I/O connection they require. Third, the mounting of the cable connectors on the rear of the backplane means that the backplane must sit sufficiently forward in the rack to accommodate their presence. This limits the usable depth of rack and, by extension, the width of the modules which may be plugged into the backplane.
One solution which has been tried is to extend the height of the backplane and to design the layout of the backplane such that the cable connectors are mounted on the front of the backplane. This design, however, retains the limitation that the number and type of cable connectors is fixed.
The present invention is directed to an improved shelf for housing PCPs. A backplane located at the rear of the shelf is provided with an edge connector along its top or bottom edge. A variety of different modules containing different cable connectors are adapted for insertion into the backplane edge connector such that they are positioned vertically above or below the backplane. The modules having different types of cable connectors of differing widths may be interchangeably inserted into the backplane edge connector. The difference between the width of the module and the width of the backplane is such that a multiple number of modules may be inserted into the edge connector. The selection of which connector modules are inserted into the backplane is dependent upon the type of connectors required. The backplane may be configured such that the modules face either forward or rearward.
Advantageously, the number and type of connectors needed for any particular configuration of modules within the shelf does not need to be predetermined. Instead, the appropriate connector modules may be plugged into the backplane after the shelf has been installed and the modules within the shelf have been plugged in.
Also advantageously, the number of I/Os available in a standard sized rack may be increased.
Additionally, the density of connectors on a connector card can be adapted to meet user requirements without the need to alter the backplane or other elements of the system in any way.
Further, since the backplane may sit more rearwardly in the shelf, the size, and consequently the functionality, of the PCPs which connect into the backplane may be increased.
The invention may be summarized according to a first broad aspect as a shelf for housing printed circuit boards comprising an open front; a pair of sides extending from a rear to the open front of the shelf, the sides being spaced apart at opposite ends of a shelf space; a backplane extending across the rear of the shelf; a plurality of side-by-side receiving stations located in the shelf space for printed circuit boards to be received through the open front for connection to the backplane; at least one connector module releasably electrically connected to the backplane and extending vertically from and substantially parallel to the backplane; the connector module having a plurality of connectors which extend in a front to rear direction of the shelf.
The invention may be summarized according to another broad aspect as a connector module adapted for connection to a backplane comprising: a printed circuit board; a plurality of cable connectors mechanically and electrically connected to the printed circuit board and extending substantially perpendicular to the printed circuit board; an edge connector mechanically and electrically connected to an edge of a printed circuit board; the edge connector adapted to releasably mate with an edge connector on the backplane such that the module extends vertically from and substantially parallel to the backplane.
The invention may be summarized according to a further broad aspect as a backplane and connector module assembly for use with a shelf for housing printed circuit boards comprising at least one connector module releasably electrically and mechanically connected to the backplane and extending vertically from and substantially parallel to the backplane; the connector module having a plurality of connectors each of which extends in a front to rear direction of the backplane.
Other aspects and features of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.